The dangers of infection from accidental contact with the pointed end of used hypodermic needles has log been recognized and is well documented. For example, refer to Jagger, Hunt, Brand-Elnaggar and Pearson, the New England Journal of Medicine, August 1988. In most procedures, the greatest avoidable risk of accidental needle puncture, or "needle-stick", occurs during handling of the used needle, when it is generally inserted into a protective sheath for disposal. This action usually requires moving the hand which holds the sheath towards the pointed tip of the needle, and any inaccuracy in this operation raises the possibility of a puncture. The risk of this is greatly increased if the operator is working Under stress, such as time-pressure or fatigue, or is handicapped by marginal eyesight or unsteady hands.
U.S. Pat. Nos. 5,322,517 and 5,328,482 describe needle guards that are essentially "free floating" in that they are stored at the base of the needle and lock to the needle when deployed from the base to the tip of the needle to occupy a covering protective position.
The protective guard preferably is stored prior to use at the base of the needle. In this position it may further be contained within the usual protective sheath which covers a needle prior to use, and may thereby be supplied with the needle in its sealed and sterilized package.
By reason of the fact that the protective guard may be stored on the needle prior to the normal use of the needle, and occupies an insignificant, compact space, its presence produces a minimum interference with the normal use of the needle. In one application the protective guard may be stored adjacent to or even within the enlarged base of a catheter, in an unobtrusive manner that allows the catheter to be inserted in the normal manner.
After withdrawal of the needle following use, the tip of the needle can be immediately covered with the protective guard by a simple manual action of gripping the protective guard with the fingers, sliding it out of its storage position at the base of the needle, and continuing the sliding motion along the needle shaft until the guard just over-reaches the end of the needle. There it automatically locks in position with the tip of the needle safely covered inside the protective guard.
The protective guard may be slid to the needle tip by the direct application of fingers to the guard. Alternately, handle means may be provided either in the form of an arm, or the like, attached to the guard body; or by use of a simple draw string that is initially stored on the protective guard by being wrapped around its exterior casing.
The protective guard achieves its locking effect by being provided with an internal energy storage element, such as a spring, that is capable of initiating a clamping force through a clamping mechanism. This clamping force is applied directly to the exterior surface of the needle shaft. A latching mechanism serves to suspend initiation of the clamping force prior to withdrawal of the needle tip within the protective guard.
A trigger system releases the latching mechanism once the needle tip passes within the protective guard, thereby initiating the clamping force which is applied to the needle, and thereby locking the protective guard in place over the needle tip. These functions occur automatically and enclose the needle tip with a protecting means which is non-removably engaged thereto.
The clamping force need only immobilize the protective guard against axial or longitudinal displacement on the needle. Further, its locking resistance need not be symmetrical. It is essential to have a high locking resistance against further removal of the guard from the needle. In the other direction resistance to the reemergence of the needle tip from the guard can be substituted or supplemented by arranging for an occluding element to occupy the path of the needle and serve as a containment means. Once the tip enters the guard the presence of such a blocking element ensures that the needle tip cannot re-emerge from the guard even where the locking resistance against displacement of the guard towards the needle base is overcome. When such a blocking element is present, it is sufficient for the clamping mechanism to provide only a uni-directional or one-way resistance to further removal of the guard from the needle.
The present invention addresses one of the classes of mechanisms by which a needle guard of such type may engage with a needle.
The invention in its general form will first be described, and then its implementation in terms of specific embodiments will be detailed with reference to the drawings following hereafter. These embodiments are intended to demonstrate the principle of the invention, and the manner of its implementation. The invention in its broadest and more specific forms will then be further described, and defined, in each of the individual claims which conclude this Specification.